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• I wasn't sure if this would be the right place for a topic like this so sorry if it isn't.
I'm currently working on a project for Uni using FreeGLUT to make a simple solar system simulation. I've got to the point where I've implemented all the planets and have used a Scene Graph to link them all together. The issue I'm having with now though is basically the planets and moons orbit correctly at their own orbit speeds.
I'm not really experienced with using matrices for stuff like this so It's likely why I can't figure out how exactly to get it working. This is where I'm applying the transformation matrices, as well as pushing and popping them. This is within the Render function that every planet including the sun and moons will have and run.
if (tag != "Sun") { glRotatef(orbitAngle, orbitRotation.X, orbitRotation.Y, orbitRotation.Z); } glPushMatrix(); glTranslatef(position.X, position.Y, position.Z); glRotatef(rotationAngle, rotation.X, rotation.Y, rotation.Z); glScalef(scale.X, scale.Y, scale.Z); glDrawElements(GL_TRIANGLES, mesh->indiceCount, GL_UNSIGNED_SHORT, mesh->indices); if (tag != "Sun") { glPopMatrix(); } The "If(tag != "Sun")" parts are my attempts are getting the planets to orbit correctly though it likely isn't the way I'm meant to be doing it. So I was wondering if someone would be able to help me? As I really don't have an idea on what I would do to get it working. Using the if statement is truthfully the closest I've got to it working but there are still weird effects like the planets orbiting faster then they should depending on the number of planets actually be updated/rendered.

• Hello everyone,
I have problem with texture

• Hello everyone
For @80bserver8 nice job - I have found Google search. How did you port from Javascript WebGL to C# OpenTK.?
I have been searched Google but it shows f***ing Unity 3D. I really want know how do I understand I want start with OpenTK But I want know where is porting of Javascript and C#?

Thanks!
• By mike44
Hi
I draw in a OpenGL framebuffer. All is fine but it eats FPS (frames per second), hence I wonder if I could execute the framebuffer drawing only every 5-10th loop or so?
Many thanks

• By cebugdev
hi all,
how to implement this type of effect ?
Also what is this effect called? this is considered volumetric lighting?
what are the options of doing this?
a. billboard? but i want this to have the 3D effect that when we rotate the camera we can still have that 3d feel.
b. a transparent 3d mesh? and we can animate it as well?

2. how to implement things like fireball projectile (shot from a monster) (billboard texture or a 3d mesh)?

Note: im using OpenGL ES 2.0 on mobile.

thanks!

# OpenGL OpenGL camera motion in a 3D application

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Hi, I'm doing a university project that consists of a 3D visor (that is, an application that plots in a 3D environment a certain kind of objects (like lines, points, ...) and allows navigation through them by using mouse + keyboard to see how the scene is composed from different positions). I'm using wxWidgets with an OpenGL canvas and I work with C++. Following the suggestions provided in one of Nehe's tutorials I've created two quaternions, one for the pitch and one for the heading (snippets of the code are below, I can provide the full source code to anyone willing to read it). My problem is that when I perform a rotation, the keys seems to be "locked" to the old xyz-axes, I mean, if I perform a 180° rotation around myself, the "w" key goes backward in the scene instead of forward. How can I "lock" the keys to operate on the new reference system? Thanks in advance to anyone willing to help me. Roberto << header file >>
  Quaternion heading_;
Quaternion pitch_;

GLdouble pitchDeg_;

GLPoint position_;


<< initialization in the constructor >>
  pitchDeg_ = 0.0;

position_.x_ = 0.0;
position_.y_ = 0.0;
position_.z_ = -15.0;


<< rotations are performed using the mouse >>
void
GLCanvas::OnMouse(wxMouseEvent& event)
{
GLdouble delta;
mouseX_ = event.GetX();
mouseY_ = event.GetY();

if(event.Dragging()) {
if(mouseX_ < centerMouseX_) {
delta = GLdouble(centerMouseX_ - mouseX_);
}
if(mouseX_ > centerMouseX_) {
delta = GLdouble(mouseX_ - centerMouseX_);
}
if(mouseY_ < centerMouseY_) {
delta = GLdouble(centerMouseY_ - mouseY_);
ChangePitch(-0.01 * delta);
}
if(mouseY_ > centerMouseY_) {
delta = GLdouble(mouseY_ - centerMouseY_);
ChangePitch(0.01 * delta);
}
Refresh(false);
}
}


<< keyboard is used for translations/strafe >>
void
GLCanvas::OnKeyboard(wxKeyEvent& event)
{
switch(event.GetKeyCode()) {
case WXK_UP:
ChangePitch(3.0);
break;
case WXK_DOWN:
ChangePitch(-3.0);
break;
case WXK_LEFT:
break;
case WXK_RIGHT:
break;
case (int)'w':
position_.z_ += 0.3;
break;
case (int)'s':
position_.z_ -= 0.3;
break;
case (int)'a':
position_.x_ += 0.3;
break;
case (int)'d':
position_.x_ -= 0.3;
break;
case (int)'z':
position_.y_ -= 0.3;
break;
case (int)'x':
position_.y_ += 0.3;
break;
case (int)'b':
break;
default:
event.Skip();
break;
}
Refresh(false);
}


<< perform rotation + translation and plot two teacups >>
void
GLCanvas::Render()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

/**
Roto-translation matrix
**/
GLdouble rotMatrix[16] = { 1.0, 0.0, 0.0, 0.0,
0.0, 1.0, 0.0, 0.0,
0.0, 0.0, 1.0, 0.0,
0.0, 0.0, 0.0, 1.0 };

glMatrixMode(GL_MODELVIEW);

RotateCamera(rotMatrix);
glMultMatrixd(rotMatrix);

TranslateCamera(rotMatrix);
glMultMatrixd(rotMatrix);

glColor3d(1.0, 0.0, 0.0);
glutWireTeapot(3.0);

glPushMatrix();
glColor3d(0.0, 1.0, 0.0);
glTranslated(4.0, 4.0, 4.0);
glutWireTeapot(3.0);
glPopMatrix();

glFlush();
}


<< camera rotation obtained through quaternions >>
void
GLCanvas::RotateCamera(GLdouble* rotMatrix)
{
Quaternion tmp;

pitch_.CreateFromAxisAngle(1.0, 0.0, 0.0, pitchDeg_);

tmp.CreateMatrix(rotMatrix);
}


<< camera translation -- I chose to perform it by hand >>
void
GLCanvas::TranslateCamera(GLdouble* rotMatrix)
{
rotMatrix[12] = position_.x_;
rotMatrix[13] = position_.y_;
rotMatrix[14] = position_.z_;
}


<< pitch movement >>
void
GLCanvas::ChangePitch(GLdouble degrees)
{
pitchDeg_ += degrees;

if(pitchDeg_ > 360.0)
pitchDeg_ -= 360.0;
if(pitchDeg_ < -360.0)
pitchDeg_ += 360.0;
}


void
{
if((pitchDeg_ > 90.0 && pitchDeg_ < 270.0)
|| (pitchDeg_ < -90.0 && pitchDeg_ > -270))
else

}


[Edited by - roby1984 on July 24, 2008 1:27:59 PM]

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This should be a pretty easy problem to solve, but could you edit your post and enclose your code in [source] tags? That'll make it much easier to read.

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I'm sorry for having skipped code tags... Might someone help me now, please?
Roberto

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The problem is that you camera is translating in world cordinates and not in local. While I may know the problem unfortunately I don't know the solution as I am currently experiencing the same issue. I will keep returning to see if a solution is posted, and if I find one I will post it here. Sorry I can't help more than that and good luck!

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I've thought the same thing, now I'm having troubles with the remote loading of the displayed objects, but as soon as I'll fix this I'll try to find out a solution for the rotation problem (and, in that case, I will post it here). Thanks for your reply!

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I've found a tutorial written by Philipp Crocoll on CodeColony (http://www.codecolony.de/), it's the "advanced camera" example. I've studied it thoroughly, made some improvements and it worked (or, at least, now it seems to work!!).
I've put my application's source code here:
http://roby1984.netsons.org/3DVisor-0.0.3.tar.gz
(if you're interested in what my application is, just have a look at the other thread I've opened on this forum, "fglrx + OpenGL display lists - segmentation fault (long post)")
You're probably interested in GLCanvas.cc and GLCanvas.hh under the src/ directory (they lack some comments, but I've just terminated the tests of the new camera motion and I've thought you were impatient to have a solution to the problem, however my source code + the tutorial + the tutorial's source code should suffice to understand how the camera works...)
Hope this helps!
Roberto